In printing presses such as web-fed offset rotary presses, the printed products often have to be folded. To that end, the printed webs are guided through a folding former and provided with a first fold, which is known as the longitudinal fold. Subsequently, the web is cut in the folder and provided with a further fold known as the first transverse fold. Webs are frequently laid on top of one another and web streams are guided via the folding former. If said streams are cut and fed to the transverse folding apparatus, it is possible to gather the cut printed products. At this point, depending on the desired end product, great differences may occur in the thickness of the printed products which are optionally to be provided with a second longitudinal fold.
While the first longitudinal fold and the first transverse fold do not require the web sections or web to be folded to be stopped, to produce the second transverse fold the product is to be guided through between two folding rolls and has to be stopped beforehand. A folding blade then pushes the folded product between the rotating folding rolls.
The folding rolls have to be at a well-defined distance in accordance with the thickness of the product to be folded. This requires the folding rolls to be adjusted to the thickness of the product that is to be folded. To that end, it is necessary to know the thickness of the product to be folded in order to adjust the folding rolls accordingly.
Conventionally, the product thickness or layer thickness has been measured manually, for example, using micrometers or similar instruments. The folding rolls for the third fold are then adjusted manually or by means of manual positioning commands from actuating drives in the machine that makes the third fold.